1. Field of the Invention
The invention relates to N-substituted benzothiazole-2-sulfonamide compounds of the general formula: ##STR5## wherein R is benzothiazolyl or substituted benzothiazolyl represented by the general formula: ##STR6## where X represents halogen, lower alkyl, alkoxy, acetamido or nitro; R' is hydrogen, alkyl, cycloalkyl, benzyl, phenyl, naphthyl, R"--S--, or substituted aryl radical represented by the general formula: ##STR7## Y being halogen, lower alkyl, or nitro; R" is alkyl, cycloalkyl, benzyl, trichloromethyl, phenyl, naphthyl, or substituted aryl represented by the general formula: ##STR8## where Z represents halogen, lower alkyl, nitro or carboxy.
The invention further relates to a method of preparing the inventive compounds as well as to the use of these compounds as scorch retardants in rubbers and like materials.
2. Description of Prior Art
The N-substituted benzothiazole-2-sulfonamides of the invention strongly prevent prevulcanization of rubber compounds containing sulfur or sulfur donor curing agents and accelerators both in natural or diene synthetic rubbers.
In the rubber industry, it is very important to prevent scorching (or prevulcanization, burning, premature vulcanization) so as not to form scrap rubber and to make products with good physical properties.
The conventional method of preventing scorching in rubber compounds relies upon the use of a delayed action type accelerators such as benzothiazole-2-sulfenamides and further makes use of retardants such as phthalic anhydride or N-nitrosodiphenylamine.
These retardants are not satisfactory, because conventional organic acids reduce the effectiveness of sulfenamide accelerators by extending the time of vulcanization, and because the physical properties of the rubber products formed are not very good.
N-nitrosodiphenylamines become less effective when active carbon black is used, since carbon black absorbs N-nitrosodiphenylamines. By way of contrast, as a result of extensive screening tests of various kinds of organic compounds, we have found that the inventive N-substituted benzothiazole-2-sulfonamides are very effective for retarding prevulcanization when used in relatively small amounts compared with the conventional scorch retardants described above.
Halogen containing rubber compounds are cured by adding metal oxide, such as zinc oxide, substituted thiourea, polyamines or its derivatives, and recently, trithiocyanuric acid or 2-substituted-4,6-dimercapto-S-triazines.
Using these conventional vulcanization techniques, halogen containing rubber compounds are not only scorched, but also the vulcanization does not occur rapidly such that the end point of vulcanization is not sharply defined.
Besides the above mentioned retardants, some disulfides such as dibenzothiazyl disulfide (MBTS), tetramethylthiuram disulfide (TMTD) or N-cyclohexylbenzolthiazyl-2-sulfenamide (CBS) previously used as vulcanization accelerators for diene rubbers, have also been used as retardants, but in this case not only must large quantities be added; but the physical properties of the vulcanized rubber are inferior.